Jamie,
It looks like you are on your way to getting the support you need already which is great. Still I thought it might be useful for you to know how my LOCAH is being managed in my pregnancy (I'm currently 37 1/2 weeks pregnant).
Prior to falling pregnant I was on 2.5mg x 2 a day of prednisolone (deltacortril). I have been told to remain on this dose. Pred is a good steroid to take in pregnancy as it does not cross the placenta as readily as dex (we had genetic testing done prior to pregnancy to check the likelihood of baby also having CAH & these came out very low - hence we are wanting to avoid my extra steroids passing over to baby).
In terms of stress dosing during labour my endocrinologist has advised the obs team that I will need 100mg hydrocortisone every 6 hrs during active labour. Admittedly they described this as a precaution but said it was a sensible one to take. So DO ask them to seek guidance from experts in the area.
Congratulations on your baby to be & hope all goes smoothly.
Amy xx